摘要:

AbstractThe lipase‐catalyzed intresterification of triglycerides and fatty acids inn‐hexane was studied. Initially, lipase Saiken was modified with a surfactant of sorbitan esters so that its dispersibility in hydrophobic organic media was improved. The surfactant‐modified lipase formed in the modification process carried out in a buffer solution has 1,3‐positional specificity and predominantly catalyzed the interesterification reaction in a microaqueousn‐hexane system. The modification technique converted inactive lipases to very active biocatalysts for the interesterification of triglycerides and fatty acids. The pH and the weight ratio of surfactant to enzyme used during the lipase modification process have shown significant effects in determining the recoveries of the protein and enzyme activity from the buffer solution, the protein content of the modified lipase complex after being freeze dried, and the interesterification activity of the complex. The water content in the reaction solution has strongly influenced the enzyme activity as well as the distribution of the products. © 1995 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260450302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAnticariogenic casein phosphopeptides (ACPP) contain the cluster sequence ‐Ser(P)–Ser(P)–Ser(P)–Glu–Glu‐ and have commercial potential as toothpaste, mouthwash, and food additives for the prevention of dental caries. In an approach to develop a commercial‐scale process for the production of ACPP we have comprehensively characterized casein phosphopeptides (CPP) produced under industrially relevant conditions. Sodium caseinate (10% w/v) was hydrolyzed by Novo trypsin (commercial grade) at 50°C for 2 h and CPP were purified from the acid clarified hydrolysate by a single‐step selective precipitation procedure involving Ca2+(20 mol/mol casein) and ethanol (50% v/v) at pH 4.6 or 8.0. The individual peptides of the CPP preparations were purified by reversed‐phase high‐performance liquid chromatography (HPLC) and then identified by amino acid composition and sequence analyses. The yield of the pH 8.0 precipitate (13.85 ± 0.48 wt % of the caseinate) was slightly higher than that of the pH 4.6 precipitate (11.04 ± 0.30 wt % of the caseinate). However, the pH 4.6 precipitate contained predominantly (86.4 mol %) ACPP cluster peptides with small amounts of the diphosphorylated peptides (13.6 mol %), αs1(43–58) and αs2(126–136). In the pH 8.0 precipitate the cluster peptides represented a smaller proportion of the total peptides (61.9 mol %) due to increased recoveries of the diphosphorylated peptides (24.4 mol %) as well as the additional recovery of the monophosphorylated peptide β(33–48) (13.7 mol %) indicating increased cross‐linking by Ca2+at the higher pH. The recovery of the ACPP from the original caseinate was similar for both the pH 4.6 and 8.0 precipitates. Slight chymotryptic activity was detected in the industrial‐grade enzyme, resulting in minor truncation of some peptides. Also some deamidation and methionine oxidation of one peptide, αs1(59–79), were detected. In conclusion, ACPP can be produced under industrially relevant conditions with only minor modifications such as slight truncation, deamidation, and methionine oxidation. However, in order to prepare casein phosphopeptides predominantly containing the cluster sequence ‐Ser(P)–Ser(P)–Ser(P)–Glu–Glu‐, the single‐step selective precipitation with Ca2+/ethanol should be performed at pH

ISSN:0006-3592    

DOI:10.1002/bit.260450303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTo achive the coarse purification of a monoclonal antibody from whole hybridoma fermentation broth a fluidized bed cation exchange process was used. The procedure consisted of application of the crude sample and washing of the bed in a fluidized mode and elution in a fixed bed mode. A completely clarified eluate was obtained with purification factors between 4 and 8 and a concentration of the desired product (monoclonal antibody) by a factor of more than 3 was achived. Thus, a combination of the three early steps of the downstream process clarification, concentration and coarse purification was possible. Two different materials were tested: a commercially available agarose‐based matrix (Stream‐line‐SP), and a self‐derivatized material based on controlled‐pore glass (Bioran). Initial experiments were performed to describe the fluidization of the glass material. Comparison with the agarose material showed several differences, the agarose matrix allowing liquid flow closer to plug flow than the glass material. Increased backmixing in the liquid phase was detected when fluidizing the glass adsorbent compared with the agarose‐based matrix. Despite this fact, comparison of the two materials with respect to antibody binding and elution demonstrated a similar performance. © 1995 John Wil

ISSN:0006-3592    

DOI:10.1002/bit.260450304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAnerobic biofilms with dominantly acidogenic bacteria were grown in fixed‐bed recycle reactors. The influence of calcium concentration in the culture medium on biofilm mass accumulation, immobilized calcium concentration, and biofilm‐specific activity was investigated. The results indicate that the biofilm mass accumulation was increased by the presence of calcium in the growth medium when calcium concentration was not higher than 120mg/L. Calcium accumulated in the biofilms increased in proportion to the calcium level in the feed. The biofilms for an increased input calcium concentration showed a trend of decrease in specific activity. The biofilms with a thickeness of less than 0.5 mm had the highest specific activity. The optimum calcium concentration for substrate consumption by the biofilms was 100 to 120 mg/L. The biofilms transferred from higher calcium medium to lower calcium medium were more susceptible to sloughing from their support surfaces, which indicates calcium's role in the stability of the biofilm structure. © 1995 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260450305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed‐batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H13CO3−pulses and measurement of12CH4and13CH4production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO2/CH4production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively highKsvalue of 2.5 mmol m−3, it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two‐stage degradation and double Monod kinetics, both for CO2and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. © 1995 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260450306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractBatch culture conditions were established for the formation of H2‐driven whole‐cell soluble or particulate methane monooxygenase (sMMO or pMMO) activity in the obligate methanotroph,Methylosinus trichosporumOb3b, to expand its potential uses in groundwater bioremediation and the production of specific chemicals. Addition of either Ni and H2to a nitrate‐containing minimal salts growth medium or Ni and Mo to a nitrate‐lacking growth medium (induces a nitrogenase that generates intracellular H2) markedly enhanced both the hydrogenase and the accompanying washed‐cell H2‐driven MMO activities of shake‐flask cultured cells. For sMMO containing cells, H2provided in vitro reducing power for the oxidation of chlorinated solvents such as chloroform and trichloroethylene. Cell cultivations under N2‐fixing conditions in a 5‐L bioreactor, however, required an initial nitrate concentration of at least 1 to 2 mMto achieve high biomass yields (5 to 7 g of dry cell wt/L) for cells producing H2‐driven sMMO or pMMO activity. Elevation of the initial medium nitrate concentration to 20 mMshortened the culture time for pMMO producing cells by 40%, yet still generated an equivalent growth yield. High nitrate also shortened the culture time for sMMO containing cells by ∼25%, but it lowered their biomass yield by 26%. Upon storage for 5 weeks at room temperature, washed resting‐state cells retained 90% and 70% of their H2‐driven sMMO and pMMO activity, respectively. This makes their practical use quite feasible. ©

ISSN:0006-3592    

DOI:10.1002/bit.260450307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractDisposal of sludge from deinking mills represents a significant proportion of operating costs. Bioconversion of the cellulosic fraction of deinking sludge (DIS) to ethanol greatly reduces disposal costs while producing an environmentally friendly fuel. In this study, the cellulosic fraction of newsprint and deinking sludge was hydrolysed to produce fermentable sugars. For newsprint, a particle size of 1 to 1.5 mm provided optimal reaction rates in batch reactors over practical hydrolysis times, and reducing sugar concentrations as high as 35 g/L could be achieved using a fed‐batch reactor configuration. For both newsprint and DIS, the hydrolysis rate increased nonlinearly with enzyme loading. Tween‐80 only marginally improved sugar production but was able to release sugars from cellulosic substrates in the absence of lytic enzymes, in an amount proportional to the surfactant concentration and the substrate particle size. DIS was relatively recalcitrant to enzymatic hydrolysis, possibly due in part to inhibition by hydrophobic constituents. © 1995 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260450308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractHigh cell density fermentation studies were performed to produce the B subunit ofEscherichia coliheat‐labile enterotoxin (LTB) from aVibrio choleraeculture that carries a recombinant plasmid with an ampicillin resistance gene,tacpromoter, and the gene encoding LTB. Upon induction with isopropyl‐β‐D‐thiogalactopyranoside (IPTG) the culture secreted the protein into the extracellular milieu. Fed‐batch fermentation with stepwise addition of a total of 5 mMof IPTG during the active growth phase of the organism resulted in the production of 400 mg/L of LTB in 9 h and a cell optical density (OD) of 24. The LTB was purified to homogeneity with 70% recovery from the fermentation broth and was found to be chemically and biologically identical to the native protein byN‐terminal amino acid sequencing and receptor binding assay. © 1995 John Wi

ISSN:0006-3592    

DOI:10.1002/bit.260450309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFilamentous cell cultures derived from female gametophytes of the temperate brown macroalgaLaminaria saccharinawere photolithotrophically cultivated in artificial seawater medium within an illuminated 1.3‐L stirred‐tank bioreactor at 13°C using CO2in air as the carbon source. A Monod model adequately described light‐saturated growth. The apparent half‐saturation constant (Ko) was 23 μE/m2‐s, and maximum specific growth rate was 0.15 day−1. At a constant inoculation cell density of 50 mg DCW/L, biomass productivity after 26 days of cultivation increased from 630 mg DCW/L at 18 μE/m2‐s to 890 mg DCW/L at 228 μE/m2‐s. At 98 μE/m2‐s, 1.1 vvm aeration rate, and 250 rpm impeller speed, the CO2transfer rates (CO2TRs) and CO2consumption rates (r co 2) were determined over the cultivation period. At peak CO2demand, the maximum CO2TR was 0.19 mmol CO2/L‐h, butr co 2was only 0.15 mmol CO2/L‐h, implying that the culture was not CO2transport limited. This is the first reported bioreactor cultivation study of cell cultures derived from a macrophytic marine

ISSN:0006-3592    

DOI:10.1002/bit.260450310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractBiotransformations catalyzed by free and immobilized enzymes have been carried out in aqueous suspensions with up to 25% (w/w) precipitated substrate or product. For the kinetically controlled synthesis ofN‐Acetyl‐Tyr–Arg–NH2with up to 0.8Minsoluble activated substrateN‐Acetyl–TyrOEt catalyzed by α‐chymotrypsin (EC3.4.21.1) the dipeptide yield was found to be>90%. This and the space‐time yields were higher than those observed for one‐phase aqueous systems and much higher than in systems where the insoluble substrate had been solubilized by addition of organic solvents. In the equilibrium controlled hydrolysis of 0.4MD‐phenylglycine‐amide catalyzed by immobilized penicillin amidase (EC 3.5.1.11) the product precipitates. The enzyme immobilized in the support with the smallest pores could be reused without reduction in the rate due to precipitation in the pores. This decreases the number of immobilized enzyme molecules that can be used as biocatalysts. The latter was observed for supports with larger pores as the solubility decreases with increasing particle size. These results demonstrate that biotransformations with insoluble substrates or products using free or immobilized enzymes can be easily carried out in aqueous two‐phase systems, without organic solvents, provided that the pore sizes of the supports are sufficiently small and that the rate of mass transfer from the precipitated substrate is large. The latter increases with decreasing particle size. ©

ISSN:0006-3592    

DOI:10.1002/bit.260450311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY